ByBruce Allen, Bruce Allen is a regular reviewer for the Monitor.February 15, 1984

Although he was known to his contemporaries as a learned and serious poet, Giovanni Boccaccio (c. 1313-1375) is best remembered for a work notorious for its eroticism and cynicism. Only literary specialists are familiar with Boccaccio's large outpouring of lyrical and narrative poetry and prose fiction, much of which was genuinely innovative. Even the specialists pay comparatively little attention to the scholarly works in Latin to which he devoted his later years.

But the ''Decameron,'' written in Italian probably between 1351 and 1353, is one of Western literature's imperishable works. It stands beside the ''Divine Comedy'' of Boccaccio's countryman (and master) Dante Alighieri, and Geoffrey Chaucer's ''Canterbury Tales'' (which it surely influenced), as one of the seminal books of the Middle Ages. It was a work that broke with the classical tradition; its scheming, self-absorbed heroes and heroines in no way resemble the plaintive nymphs and piping shepherds of pastoral romance; its vigorous prose rhythms render the feel and flow of ordinary life with unforgettable, unheroic vividness.

In a way, this may be literature's first essentially democratic masterpiece: It reflects the recently achieved economic and social power of the merchant middle classes, and it implicitly (sometimes explicitly) mocks the traditional notion that the nobility and clergy are beings made of a finer clay than are ordinary mortals. The world of the ''Decameron'' is an arena of conflict in which ingenuity and perspicacity are the highest virtues, and in which those who have the courage to seek what they want often get it.

The ''Decameron,'' of course, consists of 100 tales told by seven women and three men during 10 days they spend in the country away from the city of Florence, then (the year is 1348) besieged by ''a death-dealing pestilence.'' The enormous work is skillfully unified, not just by the frame that encloses its stories, but by this further internal organizing device: The characters ''elect'' one of their number to ''rule'' each day of storytelling, and, except for the first and ninth days, when tellers are free to choose their subjects, each day is given a theme.

Thus, we hear stories of lovers outwitting adversity or succumbing to it, of ''the tricks that often women play men or men women or men one another,'' and, after numerous other permutations, ''of whoso has in any way wrought generously or magnificently in matters of love or otherwhat.'' The constant theme is the intricately adventurous nature of amorous desire, and the movement of the tales is toward a compassionate acceptance of human imperfection and frailty. To us, the attitude may seem perfectly common-sensical; in its time, it was revolutionary.

Small wonder, really, that the ''Decameron'' was beloved by the middle classes but snubbed by the aristocracy. Besides providing a vast, brilliantly detailed, realistic picture of Florentine life, these endlessly appealing stories confront, head-on, some ineluctably primary facts about human nature. They're like folk tales, in which people live by their wits and are never permanently affected by the misfortunes that befall them; they seem, rather, always to land on their feet. Deception and stratagem are all: Kings or nobles are frequently beset by commoners; ''the perverse hypocrisy of the religious orders'' seldom goes unpunished; thieves profit by outwitting, not overpowering, their victims; seducers find ingenious ways to avoid paying for their offenses or manage to throw blame onto others.

The ethos is, in most cases, totally pragmatic. A woman stolen away from her husband decides she prefers her abductor; another, discovered in adultery, protests the unfairness of a law ''which is binding only upon us unhappy women.'' A victim of sudden financial catastrophe turns successfully to piracy. A merchant, having been robbed, quickly determines how to place himself in the best possible graces of the noblewoman who offers him, among other things, shelter. A jealous husband locks up his wife and stands guard outside her door; her lover enters through a hole in the roof.

Many of the stories have achieved an enduring notoriety. Most readers remember the tale of Masetto the gardener, who, by pretending to be a mute, enters the secret confidences of virtually all the nuns in the convent where he toils - or the licentious story of the monk who teaches a young innocent how ''to put the devil in hell.''

Still, and although few writers have ever surpassed Boccaccio's sexual forthrightness, the ''Decameron'' should not be remembered only for its bawdiness. The grisly tale of Lisabetta, who hides her murdered lover's head in ''a pot of basil,'' inspired one of Keats's most successful narrative poems. And Chaucer adopted from Boccaccio such vivid stories as that of the lady who deceives her husband by climbing into a pear tree to join her lover, and the tale of the long-suffering wife (''patient Griselda'') who undergoes her husband's cruel testing, and proves herself far worthier than he.

None of this is news, although the appearance of this translation is indeed worthy of notice. It's the version prepared for the Villon Society by celebrated linguist John Payne and privately printed in London in 1886, edited and revised by the eminent Boccaccio (and Dante) scholar Charles Singleton - who has, he informs us, pruned away Payne's ''Victorianisms,'' his ''tendencies to quaint and archaic diction.'' (He has also contributed dozens of fascinating explanatory notes.)

The result is a swiftly readable English prose that beautifully renders Boccaccio's highly rhetorical sentences, and also allows full emphasis to his continual use of demotic language and proverbial wisdom. Payne's style is capable of amusing indirectness and also of vigorous descriptive effects, as this picture of the ''serving-wench'' who adds an amorous trick by substituting for her mistress in bed: She was ''not overyoung, but had the foulest and worst-favoured face that was ever seen; for she had a very flattened nose, a mouth all awry, thick lips and great ill-set teeth; moreover, she inclined to squint, nor was ever without sore eyes, and had a green and yellow complexion. . . . Beside all this, she was a hipshot and a bit crooked on the right side.''

These incomparable delights are now offered in a limited edition of 2,000 sets. The volumes are gorgeously designed and printed, and sturdily bound, and it's a pity that the set is undoubtedly beyond the reach of most individual pocketbooks. One hopes that libraries will purchase it, and that the present generation of browsers will discover the ''Decameron'' anew. I can't say how much I envy those who'll be reading it for the first time.